Cardiac resynchronisation and defibrillation therapy: Advances and challenges

In patients with systolic heart failure and a wide QRS complex, cardiac resynchronisation therapy (CRT) using left ventricular (LV) pacing has been shown to enhance survival, reduce heart failure hospitalisation and enhance exercise capacity in patients with all classes of heart failure. The patient subsets most likely to benefit are those with class II–IV heart failure, LBBB and a QRS width ≥ 150 ms [1]. The application of CRT in patients with less wide QRS, non-LBBB and atrial fibrillation may be associated with less benefit. Coronary sinus placement of LV lead is the main channel of CRT delivery. This can be challenging at times during implantation, and can restrict LV pacing to suboptimal site [2]. There are post-implant complications such as LV lead dislodgment, diaphragmatic pacing and device infection. A major limitation of CRT is the problem of non-responders, which can be up to 30% of all indicated patients. The response rate could be better when a QRS width ≥ 150 ms is used as an indication for CRT. Apart from lead location and lack of enough residual viable myocardium for resynchronisation, post-implant programming may play a role in reducing non-responders. This includes adjustment of atrioventricular [3] and interventricular timing [4] and the use of fusion pacing [5], [6]. The guideline for use of implantable cardioverter defibrillator (ICD) has not substantially changed since 2008 [7]. However, the application of ICD especially for primary prevention therapy in the Asia-Pacific region has been limited not only by cost and reimbursement, but also because of controversy as to the application of the primary prevention studies to the Asian populations [8]-[10]. Both appropriate and inappropriate ICD shocks carry adverse prognosis [11], and device programming to minimise ICD therapies and ablation of ventricular tachycardia have been used either prophylactically or to treat VT/VF ICD storms. The most important problem now encountered is defibrillation lead failure by some manufacturers. This has call forth the need to develop a system of lead management that includes surveillance, programming and lead extraction for ICD leads. The Asia-Pacific Heart Rhythm Society and the Japanese Heart Rhythm Society have jointly produced a series of review and original articles of these advances and challenges in CRT and ICD, which will be presented in two separate issues. The editors are confident that the well written articles will give the state of art coverage on these important cardiac therapies.